A walk-behind lawnmower includes: a housing having front wheels and back wheels and being open at the bottom; a blade rotatably housed within the housing; and an operating handle for the operator to steer while walking. This walk-behind lawnmower can proceed while using the blade to cut grass and is appropriate for cutting grass in household yards or other narrow areas.
A walk-behind lawnmower of such description is provided with a height adjusting mechanism that is capable of adjusting the height of the housing and the blade in relation to the ground in order to regulate the mowing height. The height adjusting mechanism adjusts the heights of the front and rear wheels relative to the housing. Two adjustment systems are used. The first adjustment system involves separately adjusting the heights of the front and rear wheels relative to the housing. The second adjustment system involves adjusting the heights of the front and rear wheels relative to the housing in a linked fashion. Since the front and rear wheels are linked in the second adjustment system, height can be adjusted using a single action, the adjustment operation is simple, and this system is therefore widely used. Example walk-behind lawnmowers provided with a height adjusting mechanism of the second system are disclosed in Japanese Utility Model Registration No. 2530377, Japanese Patent No. 2599658, Japanese Patent Application Laid-Open Publication No. H06-296414, and Japanese Patent Application Laid-Open Publication No. S58-129908.
The height adjusting mechanism of the walk-behind lawnmowers disclosed in Japanese Utility Model Registration No. 2530377 and Japanese Patent No. 2599658 is provided with a front wheel-supporting member and a rear wheel-supporting member that are linked to the front and rear of the housing so as to allow up-and-down swinging; a height-adjusting plate that is linked to the upper part of the housing so as to allow up-and-down swinging; a front rod and a rear rod that convey the swinging motion of the height-adjusting plate to the front and rear wheel-supporting members; and a locking mechanism for restricting the swinging motion of the height-adjusting plate. The front wheel-supporting member supports the front wheels, and the rear wheel-supporting member supports the rear wheels.
The locking mechanism is composed of a plurality of locking grooves that is formed on the height-adjusting plate; a locking pin that can selectively interlock with one of the locking grooves; and an operating knob that is operated so as to insert and retract the locking pin in relation to one of the locking grooves. The operating knob is capable of swinging up and down.
When the operator uses the finger of one hand to swing the operating knob upward, the locking pin separates from the locking groove, and the height-adjusting plate can therefore swing up and down. The operator uses the other hand to move the housing up or down while holding the operating knob in the same position, whereby the height of the housing and the blade can be adjusted. When the hand is taken away from the operating knob after adjustment, the operating knob automatically returns to the original position, whereby swinging of the height-adjusting plate is restricted.
The height adjusting mechanism of the walk-behind lawnmower disclosed in Japanese Patent Application Laid-Open Publication No. H06-296414 is composed of a front wheel-supporting member and a rear wheel-supporting member that are linked to the front and rear of the housing so as to allow swinging up and down; a linking member for linking together the front and rear wheel-supporting members so as to allow concerted motion; and a locking mechanism for restricting the swinging motion of the rear wheel-supporting member. The locking mechanism is composed of a plurality of locking grooves formed on the rear wheel-supporting member; and an operating lever that can selectively interlock with one of the locking grooves. The operating lever extends upward from a lateral part of the housing and is capable of swinging in the widthwise direction of the mower.
When the operator uses one hand to swing the operating lever toward the widthwise center of the mower, the operating lever is separated from the locking groove, and the rear wheel-supporting member can therefore swing up and down. The operator uses the other hand to move the housing up or down while holding the operating lever in the same position, whereby the height of the housing and the blade can be adjusted. The operating lever is returned to the original position after adjustment, whereby swinging of the rear wheel-supporting member is restricted.
The height adjusting mechanism of the walk-behind lawnmower disclosed in Japanese Patent Application Laid-Open Publication No. S58-129908 is composed of parallel links for suspending the housing on a frame that includes front wheels and rear wheels; and a locking mechanism for restricting forward or backward displacement of the parallel links.
The locking mechanism is composed of a plate that extends upward from the frame; a plurality of locking grooves formed in a row from front to rear on the upper end of the plate; a locking pin that can selectively interlock with one of the locking grooves; and an operating lever that is operated so as to insert and retract the locking pin with relation to one of the locking grooves. The operating lever extends upward from the upper surface of the housing and can swing in a forward-and-backward direction. The locking pin is attached to the operating lever so as to be capable of relative displacement in the longitudinal direction of the lever. The parallel links are linked to the operating lever so as to allow concerted motion.
When the operator swings the operating lever in the forward-and-backward direction, the parallel links are displaced in the forward-and-backward direction, whereby the housing is moved up or down. The locking pin in this instance swings in the forward-and-backward direction along with the operating lever and sequentially enters into and retracts from the locking grooves according to the swinging motion. The up and down movement of the housing is restricted in states in which the locking pin is interlocked with one of the locking grooves.
The height adjusting mechanism of the second system has a comparatively complex configuration, as is made clear from the technology disclosed in Japanese Utility Model Registration No. 2530377, Japanese Patent No. 2599658, Japanese Patent Application Laid-Open Publication No. H06-296414, and Japanese Patent Application Laid-Open Publication No. S58-129908. Despite such complex configurations, greater operational reliability and durability is needed to resist the effects of the dust produced during lawn mowing. The operator may also frequently adjust the height of mowing according to the lawn-mowing conditions, and greater operability is therefore also needed for the height adjusting mechanism.